I have just noticed (thanks, Pete!) that I have been infected with the kak virus.
If you are using Outlook Express 5.0 for Windows and I have sent you email after November 2nd, you might want to run a check and install the patch provided by Microsoft.
The virus spreads by putting itself in place of the signature on the emails you send out, and will shut down Windows on the first of each month after 4 p.m.
Quick check: if the directory – usually C: – which contains your autoexec.bat has a file named ae.kak in it, you’re infected. Don’t delete that file, it is the healthy backup of your autoexec.bat!
Really sorry for the trouble.